[21136] Bugfix: Revert XML Flow controller names to `const char*`

[Mario-DL]

Description

PR #4893 introduced an ABI break changing the flow controller descriptor names to std::string. This PR reverts that change and handles the flow controller names in a collection within XMLParser. It also defines a clear() method intended to clean the collection upon XMLProfileManager destruction.

Note I introduced a mutex but I dont think it is needed 100% since the XMLParser configuration may be something sequential, but I introduced it anyways.

Important A cherry pick of this PR should be merged in the following backports

• 4905

• 4906

• 4907

Contributor Checklist

• [X] Commit messages follow the project guidelines.
• [X] The code follows the style guidelines of this project.
• NO Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
• [X] Any new/modified methods have been properly documented using Doxygen.
• [X] Any new configuration API has an equivalent XML API (with the corresponding XSD extension)
• [X] Changes are backport compatible: they do NOT break ABI nor change library core behavior.
• [X] Changes are API compatible.
• NO New feature has been added to the versions.md file (if applicable).
• [X] New feature has been documented/Current behavior is correctly described in the documentation.
  • Related documentation PR: eProsima/Fast-DDS-docs#806
• NO (see PR description) Applicable backports have been included in the description.

Reviewer Checklist

• [x] The PR has a milestone assigned.
• [x] The title and description correctly express the PR's purpose.
• [x] Check contributor checklist is correct.
• [x] Check CI results: changes do not issue any warning.
• [x] Check CI results: failing tests are unrelated with the changes.

[JesusPoderoso]

@richiprosima please test this

[JesusPoderoso]

@richiprosima please test this

[EduPonz]

@Mario-DL please remember to cherry-pick this onto the other backports

[Mario-DL]

Cherry picks added 👍🏻